A new computation of the constant that describes the strength of the force between the quarks in a proton may help theorists tackle one of the most challenging problems of physics: analytically solving the theory of QCD and determining its coupling strength at large distances.

Quantum Chromodynamics is the theory of the strong force, describing how quarks combine to make the protons and neutrons in the nucleus of the atom. While the strong force strength is known to be weak at small separation between quarks, its value and behavior at large distances is uncertain and hotly debated.

To tackle that problem, three scientists, including one based at DOE's Jefferson Lab, computed the constant that describes the strength of the force between the quarks in a proton. They computed the constant using a novel approach: the Maldacena conjecture, a method that connects QCD-like theories in physical space to gravity-like theories in a mathematical five-dimensional space.

The calculation showed that the Maldacena conjecture provides an analytical way to solve QCD. Their analysis also clarifies why different earlier calculations have yielded different values for the constant, thus giving new insights into how to consistently define strong force coupling, as well as providing new non-trivial tests of QCD.

A paper describing the result was published on May 28 in the journal *Physical Review D*.

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## MorituriMax

Heh..

## nuge

## Sonhouse

Jun 07, 2010## solidspin

it WAS a lot of very useful information...

## jsa09

## daywalk3r

Cosmological "constant" anyone? That was an analytical/statistical approach too :-|

## PinkElephant

There are lots of non-geometrical constants in physics. For instance, the gravitational constant, vacuum permittivity constant, speed of light, and mass of an electron come to mind.

Perhaps at some deeper (heretofore unknown) level all these "constants" indeed derive from structural/geometric relationships. However, lacking access to such fundamental insight we can only treat them as empirical constants, and move along.

## daywalk3r

Also that many of the currently known "constants", which are based on empirical measurements and we have yet to discover the background of, might not even be real constants at all.

Everything in the Universe is relative, there are no absolutes, so every real constant is, in fact, just a representation of a relation (or multiples of them) at some point.

Of course we don't know most of these relations yet - physics would be no fun anymore if we did, after all :) As the route to infinity is infinitively long, it is an eternal task for physics research to discover them all.

## Gene_H

http://www.hep.ph...vans.pdf

If doesn't deal with QCD calculations of force constant, but mass of proton - but the usage of Maldacena's conjecture is analogous here.

For nonformal intro into Maldacena duality this article may be interesting, too:

http://www.tinyurl.cz/rgb

## daywalk3r